Why did the ancient Maya take their sacrificial rites underground?

Inside Actun Tunichil Muknal, a giant limestone cave in the jungle of western Belize, it has been raining for thousands of years. Water falls lightly from the tips of stalactites into the river flowing through the cave. Beneath this light shower, I wade up the river with University of California, Merced, archaeologist Holley Moyes. She is 5 feet 4 inches tall, and the water reaches up to her chin, leaving a ripple in her wake as she moves deeper into the chamber. In the vast and echoing hall, our headlamp beams are like pinpoints in the pitch-black darkness. Underwater, tiny fish nibble at our legs.

Archaeologist Holley Moyes wades through the high waters of Actun Turnichil Muknal to reach artifact-laden chambers within its depths.

Benedict Kim

A quarter-mile deep in the cave, Moyes hoists herself onto a slippery ledge and leads me into a large chamber. Spread over the ground are hundreds of ancient orange and black ceramic pots, some as large as beach balls. Scattered among them are small obsidian tools, stone figurines and mirrors made of pyrite. We climb a ladder to a small chamber tucked away high above the cave floor. “There she is,” she says, as though greeting an old friend. Her headlamp illuminates a human skeleton lying on its back, its mouth jarred open, its ribs covered in glittering calcite. It is the remains of a 20-year-old woman known as the Crystal Maiden. She was sacrificed by an ancient Maya priest as part of a religious ritual more than 1,000 years ago.

Over the past 50 years, vestiges of religious rituals have turned up in hundreds of caves throughout the land of the ancient Maya, stretching from Mexico’s Yucatan Peninsula down through El Salvador. Some caves, like Actun Tunichil Muknal, or “Cave of the Crystal Sepulchre,” contain human or animal remains, as well as ceramic pots, musical instruments, jewelry, small sculptures and stingray spines, which were used for bloodletting. Others contain mysterious stone structures: altars, plaster platforms, pathways and monuments. In some caves, every chamber is adorned with this architecture — an extraordinary feat of engineering in absolute darkness.

The offerings are almost all found in the “dark zone” of caves, far beyond the “twilight zone,” which is what speleologists (cave scientists) call the parts of a cave illuminated by diffuse light. The Maya ventured into these deep spaces at great risk — in some cases traveling more than a mile underground, swimming down subterranean rivers, climbing precipitous cliffs or lowering themselves into tight hollows. Archaeologists can only access some of these places with ropes.

Moyes is part of a small, enthusiastic league of cave archaeologists in Mesoamerica who are trying to solve the puzzle of these mysterious underground artifacts. She has spent two decades crawling into jungle-choked caves, scrambling through guano and knocking her helmet against rocky ceilings, all in search of the answer to a single question: What drove the Maya to make offerings in such dark, remote places?

The territory of the ancient Maya covered much of Central America, but its heart was the heavy jungle surrounding Actun Tunichil Muknal in modern-day Belize and Guatemala. Between A.D. 250 and about 950, which archaeologists call the Classic Period, the rainforest here was home to resplendent cities. Copán, south of Actun Tunichil Muknal, housed 30,000 people. Tikal, a few hours west, held 100,000. Nearby Caracol was home to as many as 180,000. Kings filled these cities with lordly stone monuments called stelae and pyramids of gray stone. The Maya studied astronomy, composed music and wrote scroll-like books, or “codices,” in elegant hieroglyphics, the most advanced writing system in the pre-Columbian Americas. But like all civilizations, the Maya eventually fell. Their great cities were abandoned and engulfed by the forest.

Starting in the middle of the 19th century, archaeologists began pouring into the jungles to search for traces of the ancient inhabitants. One of the first things they noticed about the landscape was the abundance of caves. The Maya world, which rested on a soft, water-soluble limestone formation called karst, was like a terrestrial coral reef, perforated with thousands of cavities. There were limestone caverns gushing with subterranean rivers, dry mountain caves and water-filled sinkholes called cenotes. But few archaeologists suspected there was anything to learn from these hollows. They mapped the grand pyramids, measured the ornate palaces, sketched the hieroglyphs etched into stelae. The caves — dark, cramped and spattered with guano — were ignored.

That all changed in 1959 with the discovery of a small chamber in a cave called Balankanché, near the great Yucatán ruin of Chichén Itza. A local guide broke through a false wall in the cave, revealing a dark passageway. After a 500-foot crawl, he emerged into a hidden hollow brimming with ancient vases. The discovery, which inspired a National Geographic-funded excavation and report, made archaeologists wonder what other secrets the caves might hold.

By 1996, when Moyes first arrived in Belize as a Florida Atlantic University graduate student to participate in the Western Belize Regional Cave Project, cave studies had been recognized as a legitimate subdiscipline of Maya archaeology. Moyes, at 34, was older than most of her fellow students at the field school. She’d come to anthropology late, from a previous life running an off-Broadway theater in New York City. As she hacked through the jungle and ducked through cave mouths, she became captivated by the riddle of the subterranean offerings.

Under the tutelage of lead archaeologist Jaime Awe, Moyes came to appreciate the intricacy and depth of the Maya’s relationship to the underworld. Caves, she learned, were a recurring motif in ancient Maya art and literature: They were painted on the sides of ceramic vases, cited in songs and poems, and carved into stone monuments. “The Maya were cave-obsessed,” she says. To them, every cave was believed to be a portal into the underworld, which they called Xibalba.

For more than 1,000 years, the calcite-encrusted skeleton of a 20-year-old Maya woman called the Crystal Maiden has lain where she fell in a chamber deep within Actun Tunichil Muknal. Archaeologists believe she was sacrificed to appease Maya deities as populations plummeted.

Benedict Kim

At night in the jungle camp, Moyes read descriptions of Xibalba in the Popol Vuh, the ancient Maya creation myth. The story told of Hunahpu and Xbalanque, the Hero Twins, who journey into the underworld to do battle with the evil lords of Xibalba. What made Moyes curious was the conflicted nature of the Maya’s relationship to the underworld. Xibalba was known as “The Place of Fright,” home to monstrous figures with names like Pus Demon and Flying Scab; at the same time, it was linked to life-giving resources. The Maya people dreaded the underworld, but they could not live without it. Living in dark caves on the cusp of the underworld was Chac, the god of rain. He brandished terrible lightning bolts, and yet the Maya could not survive without the rain he brought. In the Popol Vuh, even after the Hero Twins defeated the major gods of Xibalba, they promised that the Maya people would bring them offerings.

In 1997, Moyes joined a team led by Awe that conducted a detailed survey of Actun Tunichil Muknal, the first in-depth study of the cave. They camped for three months beneath gigantic palm trees near the entrance. Each day she swam through the mouth of the cave, a giant hourglass draped with green vines. During long hours underground, Moyes helped map the cave and scour the floor for traces of the Maya. Sometimes she would record artifacts into the wee hours of the morning. “Time becomes obsolete underground,” she says. “I’d work late into the night without even noticing. Jaime would have to go find me because I’d been down so long.”

Just inside the cave mouth and within the twilight zone, the team found pots and large offerings of snail shells. As they moved deeper into the cave, the offerings grew stranger and more abundant. In the cave’s large central chamber, a quarter-mile from the entrance, they encountered a stunning profusion of artifacts: ceramic pots, grinding stones, bits of obsidian. They found more than 1,000 pieces in all. Including the Crystal Maiden, Moyes and her colleagues counted 14 human skeletons, some tucked away in corners, others splayed out in the open. At the foot of a massive speleothem, or mineral deposit, they found the remains of two young men, their skeletons dismembered and encrusted with calcite. In dark crevices, Moyes saw the skeletons of infants. They carefully extracted samples of the artifacts and pieces of charcoal from the cave floor to be carbon-dated.

Kellie Jaeger/Discover; after Thomas Miller and the Western Belize Regional Cave Project

The results revealed a puzzling pattern. The artifacts found closer to the entrance of the cave dated from A.D. 250 all the way up to the ninth century A.D. Deep in the darkness of the main chamber, on the other hand, the artifacts all dated from the eighth and ninth century A.D. Over the course of many centuries, the Maya had visited the entrance of the cave and the parts within the twilight zone, but only occasionally ventured into the dark zone. Then, during the eighth and ninth centuries, they suddenly began making frequent trips into the depths. Again and again they struck deep into the cave, leaving offerings, conducting ceremonies and performing sacrifices. And then, as abruptly as they began, the ceremonies ended. There was no sign of the Maya in the caves beyond the middle of the ninth century A.D.

This pattern matched other caves in the region. At Chechem Ha, a large, dry cave 25 miles from Actun Tunichil Muknal, Moyes found the same distribution. Ceramics and fire residue showed the cave had been visited off and on going back to the second millennium B.C., but in the eighth and ninth centuries, there was a sudden burst of activity. Even Balankanché, the cave in the Yucatán, fit the pattern: The ceramics left in the sealed chamber all dated to the ninth century.

On a quiet afternoon toward the end of that field season, Moyes sat outside the entrance of Actun Tunichil Muknal. Monkeys chittered in the trees; tanagers squawked. The river glided forth from the cave and passed over a ridge of mossy boulders, following the same path it had for millenniums. About 1,100 years ago, the Maya suddenly became fixated on this cave, venturing into the darkness again and again. What had changed, Moyes wondered, to drive the Maya into the underworld?

Some parts of the cave are only accessible by climbing — a challenging task even with modern equipment.

Benedict Kim

Classic Maya Collapse

The ninth century A.D., Moyes knew, was a turbulent time in Maya history. The great ancient cities of modern-day Belize, Guatemala and Honduras began their demise. After six centuries of legendary prosperity, the Maya heartlands suddenly emptied out. The population in Tikal, in the jungle west of Actun Tunichil Muknal, decreased from 90,000 people to 10,000. The populations of Copán and Caracol also plummeted. Maya kings, who inscribed dates on the stelae they erected, stopped building altogether: The latest date on a monument anywhere in the Maya heartland was A.D. 909. Once-glorious cities were left to be consumed by jungle. Archaeologists call this the Classic Maya Collapse.

For decades, Mayanists had debated the cause of the collapse. Some argued that the ancients were felled by a wave of foreign invaders or a deterioration of trade routes that led to economic failure. Others suggested a disease epidemic or a massive civil revolt. The strange cave offerings during the ninth century, Moyes imagined, were related to the collapse — she just didn’t know how.

In the early 2000s, the puzzle pieces began to fall into place. In 2000, a Texas-based Mayanist named Richardson Gill finished a 17-year-long study on the ancient climate of Mesoamerica. Gill examined data on sediment cores from the bottom of lakes, tree rings and cores from speleothems in caves. When he parsed the data, the pattern was unmistakable: At the beginning of the ninth century A.D., there was a sharp and severe drop in rainfall.

Moyes leads the way through one of Actun Turnichil Muknal's perilous passageways.

Benedict Kim

In his book, The Great Maya Droughts: Water, Life, and Death, Gill explains that the Maya had always had an anxious relationship with water. Between May and October of each year it rained heavily, but during the other seven months, the Maya heartland was dry as bone. To grow sufficient crops to feed their enormous populations, Maya cities relied on a network of cisterns, irrigation ditches and drainage systems that conserved rainwater from the wet months. But during the ninth century, it almost stopped raining altogether, even during the wet season.

Gill paints a grisly scene. The reservoirs and cisterns went dry. The crops, which grew in terraces cut into jungle hills, died. Starvation set in; millions perished. Eventually, the survivors gave up hope and left, migrating to the coast or to lakes in the north.

So, Moyes wondered, were the cave offerings connected to the drought? She returned to past studies on the Maya’s relationship to caves and read art history books. In one of them, she saw photographs of Maya vases. Painted on the vases were caverns in silhouette, shaped like the mouth of a monster. Inside the cave crouched a deity with wild eyes and a long headdress. It was Chac, the Maya rain god.

Etched into an ancient stone monument was another image of a cave. Floating out of the cave mouth was a rain cloud. It illustrated the ancient belief that caves, the realm of Chac, were the birthplace of rain.

Moyes also came across a photograph of a group of modern Maya — descendants of the ancient Maya who survived the Collapse — kneeling inside a cave. They held candles and were saying prayers. (Even though most modern Maya are Catholic, they continue to make pilgrimages to the caves to pray for rain and abundant crops.) It was just before the harvest, and they were conducting a ceremony to bring rain.

Carved into a rock face of the Olmec site Chalcatzingo in central Mexico, a relief known as "El Ray," shows what appears to be rain clouds emerging from a cave.

Courtesy David C. Grove

The Drought Cult

The next time Moyes swam through the shadowy mouth of Actun Tunichil Muknal, she imagined herself on the tail of a procession of ancient pilgrims. They waded through the darkness ahead of her, lighting their way with torches. On their backs, they balanced giant ceramic pots. The group moved through the cave with a choreographed slowness, chanting prayers. A priest in feathered regalia kept an obsidian blade in a sheath on his hip. A 20-year-old woman walked in the middle of the group, the river — lowered by the drought — reaching up to her waist.

The pilgrims were thin and haggard, their faces creased. In the torchlight, they eyed the stalactites, like monster’s teeth, on the ceiling. They were inside Xibalba, following the path of the Hero Twins. It was the realm of Chac. They were afraid, but they had no other choice.

The planting season was approaching, and again there had been no rain. The water reservoirs were empty, the soil in the terraced hills parched. In the cities, people whispered of leaving this place behind, perhaps heading to the coast. Their offerings to the rain god had been insufficient. But perhaps if they did something drastic, if they brought more sumptuous gifts, they could appease the god and bring rain. They watched — hopeful — as water dripped from above into the river around them.

A diagram of the relief known as "El Ray."

Courtesy David C. Grove

The pilgrims climbed into the cathedral-like main chamber. The floor was already littered with offerings from past pilgrimages. They found an empty niche to place the ceramic pots — out of some, corn spilled onto the ground. The priest sharpened his blades; the young woman trembled. In the glow of the torches, amid a rising prayer, he prepared the sacrifice.

“Just as their world was falling apart,” Moyes says, “they made a last-ditch effort to please Chac.” She calls this influx in subterranean rituals, which were happening all over the Maya world during the ninth century, the Drought Cult.

Since that first field season at Actun Tunichil Muknal 17 years ago, Moyes and her team have investigated more than 50 caves, all in Belize. “It’s still a new theory,” says University of California archaeologist James Brady, one of the pioneering cave researchers in Mesoamerica. “To claim that there was a widespread cult will require more work in the caves.”

Moyes says she plans to expand her work to sites in Mexico and Guatemala.

Ancestral Whispers

In some caves, the offerings are so elaborate and painstaking, you can almost sense the desperation and urgency the Maya felt as their world crumbled. On my last afternoon in Belize, Moyes brings me to Las Cuevas, a cave two hours south of Actun Tunichil Muknal, not far from the mega-ruin of Caracol. It is a behemoth of a cave, with an entrance big enough for an ocean liner to pass through. “During the time of the drought,” says Moyes, “pilgrims were coming here from all over.”

At the back of the first chamber, Moyes leads me to a thick stone wall made from bone-hued rocks and chunks of speleothem. Fingerprints are visible in the mortar. In the middle of the gateway is an opening, a passage so low that we have to crawl into the next chamber. The wall dates to the ninth century. “We may be looking at one of the gateways of Xibalba,” Moyes says.

In the Popol Vuh, she explains, the Hero Twins follow a road through Xibalba that brings them through separate compartments of the underworld, each characterized by a harrowing trial or challenge — not unlike the rings in Dante’s Inferno. Each compartment in Xibalba is divided by a gateway. Moyes believes the Maya may have built this gateway to re-create the Hero Twins’ path through Xibalba.

Over the next hour, we push deeper into the cave, passing through nine distinct chambers. Dividing each one is a stone gateway. On the ground in front of each portal is a sprinkling of charcoal, fallen from the torches of ancient Maya when they stopped to perform a ritual.

Through the final gateway, we emerge onto a high, craggy ledge. The path of the Hero Twins through Xibalba opens up to a view over a voluminous chamber. At the center of the chamber is a cenote; its babbling water reverberates lightly, like ancestral whispers. It takes a moment to see that almost the entire cave floor is man-made. Encircling the cenote are platforms, flat terraces of plaster — all built in the ninth century. Some terraces are still white and perfectly smooth. Looking out over the constructed subterranean landscape, I imagine thousands of desperate Maya singing and dancing on these platforms, begging for rain that would never come.

[This article originally appeared in print as "Cave of the Crystal Maiden."]